[Qt] Fix wipeclean on Windows

Reviewed by Csaba Osztrogonác.

Make sure to close the .qmake.cache file after opening it, otherwise it cannot be deleted on
a clean build because this process (build-webkit) is still using it due to Windows' exclusive
way of opening files.

* Scripts/webkitdirs.pm:
(buildQMakeProjects):

git-svn-id: http://svn.webkit.org/repository/webkit/trunk@131453 268f45cc-cd09-0410-ab3c-d52691b4dbfc
2 files changed